Question: $ \left(\dfrac{9}{4}\right)^{-\frac{1}{2}}$
Explanation: $= \left(\dfrac{4}{9}\right)^{\frac{1}{2}}$ Figure out what goes in the blank: $\Big(? \Big)^{2}=\dfrac{4}{9}$ Figure out what goes in the blank: $\Big({\dfrac{2}{3}}\Big)^{2}=\dfrac{4}{9}$ So $\left(\dfrac{9}{4}\right)^{-\frac{1}{2}}=\left(\dfrac{4}{9}\right)^{\frac{1}{2}}=\dfrac{2}{3}$